An overview of fundamentals of React

Abu Siddique
3 min readMay 7, 2021

React is the world’s most popular JavaScript library. It is an open-source, component-based, front-end library responsible only for the application’s view layer. Simply, React is an open-source JavaScript library which is used for building user interfaces. React is not a framework which tells the developer what they need rather programmer calls it where and when they need it.

React tree reconciliation is a process of algorithm which use a virtual DOM which is an in-memory representation of Real DOM when render kept the representation of a UI in memory and synced with the “real” DOM. It’s a step that happens between the render function being called and the displaying of elements on the screen.

Using react skill we can easily build a cross mobile application by React Native. React also developed by Facebook which makes it a more trustworthy and most popular JS library.

React uses JSX which is a XML-like syntax extension to ECMAScript. It basically gives us the expressiveness of JavaScript along with HTML-like template syntax. The most important thing to understand about JSX is that Babel (a JavaScript compiler that React uses) is changing JSX over to JavaScript behind the scenes.

React uses reusable, composable, and stateful UI components to develop the view. The Component simply can be defined as a function that takes props as an input and returns a JSX tree as the output.

There are two possible ways to create a component.

  1. Function Components: This is the simplest way to create a component. Those are pure JavaScript functions that accept props object as the first parameter and return React elements:
  2. Class Components: A class component requires to extend from React.Component and create a render function that returns a React element.

In React, components can call and talk to each other. When they do, they can pass information(values) between themselves as properties(known as “props”). But one thing to realize early on is that props only work in one direction. Parents can pass info to their children, but if a child needs to pass info back to its parent, you’ll need to define a function in your parent that allows the child to move information back up the chain.

React likes us to provide a unique identifier for each child component we create. This unique id is called a Keys in React. Keys are crazy important, and they can get a lot more complicated, but they’re what allows React to keep track of the unique state of tons of different components on a page.

The State is a built-in React object that is used to contain data or information about the component. A component’s state can change over time; whenever it changes, the component re-renders. The change in state can happen as a response to user action or system-generated events, and these changes determine the behavior of the component and how it will render.

Performance: React uses virtual DOM, which makes the web applications run much faster than those developed with alternate front-end frameworks. React breaks a complex user interface into individual components, allowing multiple users to work on each component simultaneously, thereby speeding up the development time.

React goes beyond simple UI design and has many extensions that offer complete application architecture support. It provides server-side rendering, which entails rendering a normally client-side only web application on the server, and then sends a fully rendered page to the client. It also employs Flux and Redux extensively in web application development.

React follows a unidirectional data flow. This means that when designing a React app, developers often nest child components within parent components. Since the data flows in a single direction, it becomes easier to debug errors and know where a problem occurs in an application at the moment in question.

React.Fragment allows you to add multiple elements without adding a bunch of unnecessary divs to the DOM.

React applications are easy to test due to a large developer community. There are dedicated tools for easy debugging from Facebook and others for browser extensions which makes the process of debugging React web applications faster and easier.

Due to the fast rendering of React applications, more and more companies are adopting this development tool, and this has subsequently led to a higher demand for React developers all around the world.